Mulching Landscape Plantings
Mulch is a very useful addition to every landscape with tree and shrub plantings. Spread it to cover the soil around your trees and shrubs.
Why to Mulch
Both organic and inorganic mulches perform many valuable and useful functions in a landscape and have many benefits beyond improving your plantings’ beauty.
Organic mulch—including pine needles, straw, wood or bark chips, or salt hay—makes your garden more attractive by providing a sense of neatness and giving your beds definition.
Inorganic mulches—such as crushed gravel, river pebbles, and porous non-woven plastic landscape fabric—control weeds and keep solar heat or winter cold from baking or freezing tree and shrub roots.
By lowering the incidence of soil-borne diseases and keeping weed growth down, mulches keep plants healthy while reducing yard care needs.
Because both insulate the soil, mulches create a favorable environment for plant roots. They keep soils warmer in the winter and cooler in the summer. In severe winter areas they reduce damage caused by harmful soil freeze-thaw cycles.
Mulches also conserve water by reducing surface evaporation. They improve soil texture by creating ideal moist conditions for worms and soil organisms. Organic mulches release nutrients and feed your trees and shrubs as they decompose.
As organic mulches slowly break down by natural biological processes, they maintain your soil’s acid-alkaline balance by adding either slightly acidic or slightly alkaline organic material to your garden’s soil.
As a general rule, pine straw, pine bark, cypress, and eucalyptus products release acidic organics, while hardwood mulches decay into alkaline compost. Take advantage by using acid-releasing mulches around acid-loving plants such as rhododendrons, and hardwood mulches around plants that like neutral or alkaline conditions.
When to Mulch
Applying mulch to the soil around your shrubs and trees mimics the conditions found in natural woodlands and forests. It preserves moisture, limits soil erosion, and moderates changes in temperature to limit frost heaving in areas with cold-winter climates and overheating in those with arid climates.
To be most successful, apply mulch as demonstrated. When reapplying mulch, remove old mulch before applying new mulch to your landscape beds. Compost or discard the removed mulch to eliminate buildup of harmful soil organisms and disease spores from your yard.
Mulch should be applied in a layer 2–3 inches (50–75 mm) deep. The top six inches of soil and mulch contains over 90 per cent of all the living soil organisms in your planting beds’ soil. Too heavy a layer of mulch deprives the soil of these necessary bacteria, worms and other beneficial life.
Water the soil before application until the soil is deeply moist, then apply mulch throughout a planting bed. Always start applying mulch at the root zones of each tree or shrub. Keep an open space of 3–4 inches (75–100 mm) between the mulch and any tree trunks or shrub branches.
A mulch-free zone around each plant helps prevent basal rot or graft canker disease at the trunks’ junction with the soil surface.
Whenever the mulch layer has decomposed and there is only 1 in. (25 mm) left—usually in 2–3 seasons— replenish it. How often renewal is needed depends on your climate and on the type of mulch you are using; typically, bark chips outlast pine needles or straw.
Apply new mulch after raking and removing the old layer rather than top-coating the existing mulch.
Step-by-Step Instructions
Mulch performs several useful functions in the landscape. Besides dressing up beds and borders it helps conserve water and blocks sunlight from weed seeds to prevent their germination. Organic mulches also decompose slowly and release beneficial nutrients that trees and shrubs need.
Garden mulches come in many forms. They include bark and wood chips, compost, salt grass hay, decomposed granite, and cocoa hulls, among others.
Gather your mulch, a garden cart, a fine-tined mulch or leaf rake, and don your garden gloves. Follow these easy steps:
How to Apply Mulch in Landscape Plantings
Rake, remove, and discard any old mulch that remains before adding new mulch. This step also removes leaf litter, insect eggs, fungal spores, and soil disease organisms.
Use a garden cart to place piles of mulch spaced throughout the to-be-mulched area.
Rake the mulch into an even layer, 2–3 in. (50–75 mm) thick. Keep the mulch at least 3–4 in. (75–100 mm) out and away from your shrub stems and tree trunks.